can you tell what has happened to my father?

[anupu]

my father is of 60+ age he was always an eccentric man since my childhood i have seen him making claims such as government is against him he is god and many more but he was still always a caring father always protected us from every problem in life he was extremely protective he is a doctor and my mother used to be ill (suffering sarciodosis) he used to treat her since last 18 years like a faithful husband should have a year back my mother passed away my father started behaving more erratically he started flirting with women most importantly with close relatives he even made advances on my sister he behaves erratically fights without a reason then claims we started the fight contradicting him is not allowed no matter what you cannot speak in front of him he delivers big speeches on how he is a good father and he was once a great father he is very angry about me shifting to another city for my college and my sister going abroad for a phd
a few of his erratic behavior is
he starts speaking on pointless topics
he has no social fear
he repeats his points again and again
he considers himself very young charming and intelligent
he will start the fights and then will claim we did even if you stay completely silent
he then after a while will become normal then again he goes berserk
he claims that people are conspiring against him just to defeat him and we are supporting them( and my mothers death is a part of it)
please help i am at my wits end please.